upstart-event-bridge

upstart-event-bridge [OPTIONS]

-d, --daemon
    Detaches from the controlling terminal and runs in the background as a daemon.

--debug
    Enables verbose debugging output to standard error (or syslog if daemonized).

--enable-dbus-daemon-bridge
    Activates the bridge for the D-Bus system bus, allowing communication with system-wide D-Bus services.

--enable-dbus-session-bridge
    Activates the bridge for the D-Bus session bus, typically used for desktop applications and user-specific services.

--name NAME
    Registers the event bridge with the specified D-Bus NAME, allowing other D-Bus clients to find and interact with it.

The upstart-event-bridge command is a daemon that acts as a connector between the Upstart init system and external event sources or sinks, primarily D-Bus. It translates events from non-Upstart systems (like D-Bus signals) into Upstart events, allowing Upstart jobs to be started or stopped based on external triggers. Conversely, it can also translate Upstart events (e.g., job starts, stops, errors) into a format understandable by external systems, such as D-Bus signals, enabling other applications or services to monitor and react to the state changes within the Upstart system. This bridge was crucial for integrating Upstart into broader desktop environments or complex server setups that relied on inter-process communication mechanisms beyond Upstart's native eventing model.

The upstart-event-bridge command is part of the Upstart init system, which has been largely superseded by systemd in most modern Linux distributions (e.g., Ubuntu, Debian, Fedora). Consequently, this command is primarily relevant for legacy systems still using Upstart. Its functionality is tied specifically to Upstart's event model and is not compatible with systemd or other init systems.

The primary function of upstart-event-bridge is to facilitate two-way communication with D-Bus. This allows Upstart jobs to be triggered by D-Bus signals (e.g., a USB device plug, network interface state change, or user session events) and enables external applications to subscribe to and react to Upstart events, such as a service starting, stopping, or failing. It essentially extends Upstart's internal event bus to the D-Bus system and session buses.

Upstart was developed by Canonical Ltd. (for Ubuntu) as an event-based replacement for the traditional System V init daemon, aiming to improve boot times and system management. upstart-event-bridge was introduced as a key component to integrate Upstart's event model with broader system communication mechanisms, particularly D-Bus, allowing for reactive service management based on external triggers. While Upstart gained initial adoption, systemd emerged as a more comprehensive and widely adopted init system, leading most major distributions to transition away from Upstart by the mid-2010s. As a result, upstart-event-bridge is now considered a legacy command, primarily found on older Linux installations.

init(8), upstart(8), systemd(1), dbus-daemon(1), dbus-send(1)